Lubricating compositions



United States Patent 3,049,493 LUBRICATING COMPOSITIONS David W. Young, Homewpod, and Jay S. Curtice, Chicago, 11]., assignors, by mesne assignments, to Sinclair Research, Inc., New York, N.Y., a corporation of Delaware N0 Drawing. Filed Sept. 6, 1957, Ser. No. 682,282

8 Claims. (Cl. 252-56) This invention relates to novel compositions of matter. More particularly, this invention is concerned with a novel synthetic lubricating oil composition adaptable for use as an aircraft turbine lubricant. The advent of prop-jet and turbo-jet type aircraft have necessitated the use of lubricating oils possessing properties of lower volatility, higher viscosity indices and lower pour points along with improved oxidation, corrosion, and thermal stability than mineral lubricating oils heretofore employed in automotive or aircraft engines of the reciproeating type.

We'have found an ester type synthetic lubricating oil composition particularly suited for these purposes and it includes a blend of an ester base synthetic lubricant and a polyester thickener. The viscosity of the compositions provided by our invention may be varied by adjusting the relative amounts of these components in the composition, for instance, to lower the viscosity, the synthetic lubricating oil to polyester thickener weight ratio is increased and conversely, to increase the viscosity, this ratio is decreased. The polyester thickener employed in these blends will increase the load carrying capacity of the synthetic lubriacting oil and will generally be not more than about 2 or 5 to 50 weight percent of the blend and preferably about to 50 weight percent. Usually the amount of the polyester thickener employed in any blend would be at least about 5 percent and advantageously the final lubricating oil compositions would have a maximum viscosity at -40 F. of about 13,000 centistokes and a minimum viscosity of about 7.5 centistokes at 210 F. V 7

Various synthetic oils of lubricating viscosity may be employed in our compositions, for instance those ranging from the light to heavy oils having viscosities of about SUS at 210 F. to 250 SUS at 210 F., and preferably about 35 to 150 SUS at 210 F. Included among the synthetic lubricants are, for example, the polyalkylene glycols prepared from alcohols and alkylene oxides. A number of these oils are available as Ucons prepared from aliphatic alcohols and propylene oxide and having molecular Weights of about 400 to 3000. Related lubricants are the higher molecular Weight alkylene oxides, polycarbonates, Acryloid polymers, formals, polyformals, polyglycidyl ethers and other ether-s.

We prefer to employ synthetic lubricating oils of the ester types, for instance the simple diesters. The simple diesters are made from alcohols and dicarboxylic' acids. Among the dicarboxylic acids employed-are those containing up to about 12 carbon atoms, particularly the aliphatic acids such as adipic, azelaic, suberic, alkenylsuccinic, sebacic, etc. The alcohols employed usually contain up to about 20 carbon atoms, preferably up to about 12 carbon atoms, and are generally aliphatic, such as the butyl, hexyl, 2-ethylhexy1, dodecyl alcohols. The alcohols can also be polyfunctional materials, such as glycols, and included among the glycolsare the ether glycols. Generally, the synthetic base oils consist essentially of carbon, hydrogen and oxygen, i.e. the essential nuclear chemical structure if formed by these elements alone. However, these oils may be substituted with other elements such as halogens, e.g. chlorine and fluorine. Among other specific synthetic oils falling within the above class are di-(2-ethylhexyl) sebacate, di-(Z-ethyl- 3,049,493 Patented Aug. 14', 1962 2 hexyl) phthalate, di(l,3-dimethyl butyl) adipate, di-(2- ethylbutyl) adipate, di-(l-ethylpr-opyl) adipate',-diethylox= alate, dicyclohexyl adipate, di-(undecyl) sebacate, di-Cel losol-ve phthalate, and dibenzyl sebacate.

The polyester thickener employed in our compositions can be prepared by direct esterification of a dibasic acid with a mixed polyoxyalkylene glycol. The dibasic acid can be any suitable aliphatic dibasic acid containing from about 6 to 11 carbon atoms, such as adipic, palmitic, suberic, azelaic or sebacic acid. The mixed polyoxyalkylene glycol is a liquid and may be represented by the following general formula:

where m, the polyoxypropylene constituent, has an average value from about 15 to 45 and (C H O) the polyoxyethylene constituents, equal about 5 to 20percent of the total weight of the compound. The polyoxypropylene constituent generally has an average molecular weight generally of from about 800 to 2500 but preferably from about 800 to 1000. Mixed polyether glyc-ols of this type are described in U.S. Patent No. 2,674,619, which also describes a method for their preparation. The branched chain central portion of the glycol molecule gives the polyester the solubility and pour characteristics necessary for a thickener stock while the straight chain ether end portions which link with the dibasic acid impart improved oxidation, corrosion and thermal stability.

The esterification reaction is conducted using about one mole of the dibasic acid with about 0.7 to 1.5 moles of the glycol but preferably this ratio is about 1 to 1 and is continued with concomitant boiling off of water from the reaction mixture. The temperature of this reaction is usually at least about 300 F. and should not be so high as to decompose the wanted product. If desired, the reaction can be conducted in the presence of'a solvent, for instance an aromatic hydrocarbon such as xylene, and to provide a better reaction rate we prefer 'to employ an acid esterification catalyst. Many of these catalysts are known and include, for instance hydrochloric acid, sul furic acid, aliphatic and aromatic sulfonic acids, phos- .phoric acid, perchloric acid, hydrob'romic acid, hydrofiuoric acid and dihydroxy fluoboric acid. Other catalysts are thionyl chloride, boron trifluoride, silicon tetrafiuoride, the chlorides of magnesium, aluminum, iron, zinc, copper and tin and salts of mercury, silver, cobalt, nickel and cerium. In the preferred reaction, when employing the dibasic acid, we use about 0.1 to 0.5 weight percent of paratoluene sulfonic acid catalyst, a xylene sol vent and a temperature of about 345 to 390 F. While boiling off .water by refluxing.

The polyester thickener can be modified by reacting it with a cyclic ether, i.e. an olefin oxide, of up to about 10 carbon atoms. The preferred oxides are the alkylene oxides of 2 to 3 carbon atoms, that is ethylene oxide and propylene oxide. In the reaction about 5 to 20 percent'of the oxide is consumed based on the w'eightof the polyester feed. The temperature of the reaction is usually at least about 300 F. to provide a satisfactory reaction rate and should not be so high as to decompose the wanted product. Preferably, we employ a' temperature from about 325 to 425 F. Advantageously, the reaction with the oxide is conducted until the acid number of the product is below about 1.0 as measured by" the ASTM-D974 procedure. Usually thereaction time required is at least about two hours and there is little-to be gained by continuing the reaction-for more thadaboiit twenty hours. Preferably, the reactionis conductedjuntil the acid number of the product is less than about'.0.2. The pressure during the reaction is sufficient to'maintain the liquid phase and can be released to cool the reaction product.

In the preferred form of the present invention the polyester thickener from the reaction of the dibasic acids with mixed polyoxyalkylene glycols is first combined with a low molecular weight alcohol of up to about 20 carbon atoms before employing the olefin oxide or alkylene oxide. Preferably, the alcohol contains up to about 12 carbon atoms. Useful aliphatic alcohols include butyl, hexyl, methyl, 2-ethylhexyl, iso-octyl, and dodecyl alcohols, C oxo alcohols, and octadecyl alcohols. We can also employ fluoro alcohols particularly those of the formula CHF (CF CH OH, such as 1,1,9-tri-H-perfluorononyl alcohol, 1,1,5-tri-I-I-perfluoropentyl alcohol, 1,1,7-tri-H- perfluoroheptyl alcohol. The amount of alcohol reacted can be about to percent based on the weight of the intermediate. The temperature of the reaction will generally be at least about 300 F. in order to obtain a satisfactory reaction rate and should not be so high as to decompose the wanted product. Preferably, the temperature will range from about 325 to 425 F. Advantageously, the reaction is conducted until the intermediate has an acid number of less than about 10, e.g. about 2 to 10, which usually requires a minimum of about two hours. There is no particular advantage associated with continuing the reaction past about twenty hours. The pressure of the reaction is sufiicient to maintain the liquid phase.

Our reactions involving the polyester and the alcohols or olefin oxides can be conducted in the presence of an aromatic solvent such as xylene. Advantageously, the solvent is in the reaction during preparation of the polyester and during the reaction of the alcohol, but unreacted alcohol and solvent are removed before employing the olefin oxide. In removing the alcohol and solvent, temperatures which decompose the product should be avoided as by distilling under a vacuum of less than 20 mms. of mercury. The polyester thickeners or the modified polyester thickeners have a kinematic viscosity ranging from about to 125 centistokes at 210 F. As noted, they are useful synthetic lubricant additives or blending components and if desired the reaction involving the alcohols and olefin oxides can be conducted in the presence of other components of the final synthetic blend desired.

When desired, our compositions, including a synthetic lubricating oil and a polyester thickener, can contain additives or components to impart wanted characteristics to the compositions. For instance, anti-oxidants, extreme pressure or load carrying agents, anti-foam agents or corrosion inhibitors can be added. We usually incorporate phenothiazine as an anti-oxidant and methyl silicone polymer having a viscosity of 60,000 cs. at 25 C. as an anti-foaming agent.

The following specific examples will serve to illustrate the compositions of the present invention.

EXAMPLE I Preparation of a Polyester Thickener 303 grams (1.5 moles) of sebacic acid, 1587 grams of a mixed polyether glycol having the general formula:

hexanol is added and the resulting mixture is refluxed for 7 hours yielding 9 grams of water. Xylene and 2- ethylhexanol are removed by vacuum distillation (maximum pot temperature 450 F. at 2 to 5 mm. Hg). The bottoms from the distillation were treated with 10 weight percent propylene oxide for 5 /2 hours at a temperature of 205 F. in a Magne-Dash unit. The pressure ranged from 135 to 160 p.s.i.g. Propylene oxide was flashed ofi by heating the product to 450 F. and stirring in an open vessel. The resulting polyester compound hereinafter referred to as polyester IA had the following characteristics:

Preparation of a Synthetic Oil Composition Containing Polyester IA A synthetic lubricant blend is prepared by blending together 71.5 parts of di-2-ethylhexyl sebacate oil with a K.V. at 100 F. of 12.3 cs., a V.I. of 154, an acid number of 0.12 and a pour below F., .001 part of methyl silicone polymer having a viscosity of 60,000 cs. at 25 C., 0.5 part of phenothiazine, and 28 parts of polyester IA. The resulting composition hereinafter referred to as composition IA had the following characteristics:

K. vis., 210 F. (cs.) 7.580 K. vis., F. (cs.) 33.53 K. vis., 40 F. (cs.) 7997 V1. 162.9 Pour F.) B-80 Acid No .06 Flash 455 Corrosion and oxidation stability (347 F., 72 hours):

Thermal stability, 10 hours at 545 F., under nitrogen:

Percent dec 0.8 Percent vis. change (100 F.) 34 Percent vis. change (210 F.) 39 Percent weight loss 3.8

EXAMPLE II Preparation of Polyester T hickener A polyester thickener was prepared in a manner simii 5. lar to that of polyester IA, except that a mixed polyether glycol had the formula:

CH3 E 4 )D"( i )m"'( 2 4 )n' where m' has an average value of 40 and (C H O) is 10 percent of the total weight of the compound. Nine hours are required to bring the first step to 94.5 percent completion and the product has a kinematic viscosity of about 55 centistokes at 210 F. 2-ethylhexanol (10 percent by weight of the reaction mixture) is added and the mixture is refluxed for 6 hours. The resulting product is stripped to 400 F. (2 to mm.), treated with propylene oxide, and flashed in the same manner previously described in Example LA above. The resulting polyester, hereinafter referred to as polyester IIA, had the following characteristics:

A synthetic lubricant blend is prepared by blending together 71.5 parts of di-2-ethylhexyl sebacate oil with a K.V. at 100 F. of 12.3 cs., a V.I. of 154, an acid number of 0.12 and a pour below 80 F., .001 part of methyl silicone polymer having a viscosity of 60,000 cs. at 25 C., .05 part of phenothiazine, and 28 parts of polyester IIA. The resulting composition hereinafter referred to as composition IIA had the following characteristics:

K. vis., 210 F. (cs.) 7.569 K. vis., 100 F. (cs.) 32.52 K. vis., -40 F. (cs.) 7650 V1. 165.6 Pour F.) B-80 Acid No 0.10 Flash 455 Corrosion and oxidation stability (347 F., 72 hours):

Steel, mg./cm. 0.015 Silver, mg./cm. 0.046

Aluminum alloy, mg./cm. 0.007

Magnesium alloy, mg./cm. 0.093

Copper, rug/cm. 0.15

Vis. change at 100 F., percent 1.91

Acid number change 1.49

SOD corrosion (325 F., 1 hour):

Lead, mg./sq. in 3.222

Copper, mg./ sq. in -0.11

Thermal stability, hrs. at

460 F., under nitrogen:

Percent decomposition 0.4

Percent vis. change (210 F.) 19

Percent vis. change (100 F.) 28

Percent weight loss 0.4 Thermal stability, 10 hrs. at 545 F., under N Percent decomposition 1.2

Percent vis. change (100 F.) 42

Percent vis. change (210 F.) 51

Percent weight loss 3.2

We claim:

1. A syntheticlubricating oil composition consisting essentially of (1) a diester synthetic oil base havinga viscosity of about 35 to 250 SUS at 210 F., said diester being of an aliphatic dibasic acid of up to about 12 carbon atoms and an aliphatic alcohol of up to about 12 carbon atoms and (2) about 5' to 50 weight percent of a polyester prepared by the reaction of an aliphatic dibasic acid containing from about 6 to 11 carbon atoms with a polyoxyalkylene glycol of the formula:

where m has an average value from about 15 to 45, (C H O) is about 5 to 20 percent of the total weight of the glycol, in the molar ratio of about 110.7 to 1.5, and continuing the reaction until the polyester product has a kinematic viscosity of about 35 to centistokes at 210 F.

2. The lubricating oil composition of claim 1 in which the diester synthetic oil base has a viscosity of about 35 to SUS at 210 F., the weight percent of the polyester is about 20 to 50, and the aliphatic dibasic acid is sebacic acid.

3. A synthetic lubricating oil composition consisting essentially of 1) a diester synthetic oil base having a viscosity of about 35 to 250 SUS at 210 F., said diester being of an aliphatic dibasic acid of up to about 12 carbon atoms and an aliphatic alcohol of up to about 12 carbon atoms and (2) about 5 to 50 weight percent of a polyester prepared by the reaction of an aliphatic dibasic acid containing from about 6 to 11 carbon atoms with a polyoxyalkyl-ene glycol of the formula:

where in has an average value from about 15 to 45, (C H O) is about 5 to 20 percent of the total weight of the glycol, in the molar ratio of about 1:07 to 1.5, continuing the reaction until the polyester product has a kinematic viscosity of about 35 to 125 centistokes at 210 F., reacting this product with about 5 to 20 weight percent, based on the polyester, of an aliphatic alcohol containing up to about 20 carbon atoms at a temperature of at least about 300 F. and below the decomposition temperature, and then reacting this product with about 5 to 20 weight percent, based on the polyester, of an olefin oxide having up to about 10 carbon atoms at a temperature of at least about 300 F. and below the decomposition temperature.

4. The lubricating oil composition of claim 3 in which the diester synthetic oil base 'has a viscosity of about 35 to 150 SUS at 210 F., the weight percent of the polyester is about 20 to 50, the aliphatic dibasic acid is sebacic acid, the aliphatic alcohol containing up to about 20 carbon atoms is 2-ethyl hexanol, and the olefin oxide is propylene oxide.

5. The lubricating oil composition of claim 2 in which m has an average value from about 15 to 18.

6. The lubricating oil composition of claim 4 in which m has an average value from 15 to 18.

7. The lubricating oil composition of claim 2 in which 8. The lubricating oil composition of claim 4 in which m has an average value from 37 to 45.

References Cited in the file of this patent UNITED STATES PATENTS 2,499,984 Beavers et a1 Mar. 7, 1950 2,628,974 Sanderson Feb. 17, 1953 2,705,724 Cottle et a1. Apr. 5, 1955 2,785,194 Hoare Mar. 12, 1957 2,820,815 Matuszak et a1. Ian. 21, 1958 (Other references on following page) 7 8 UNITED STATES PATENTS OTHER REFERENCES 2, Matuszak e a June 1 Ind. and Eng. Chem., vol; 39, No. 4, April 1947, pages 2,929,786 Young at al Mar. 22, 1960 484-491; vol, 42, No, 12, December 1950, pages 241s- FOREIGN PATENTS 5 2420.

711,211 Great Britain June 30, 1954 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 O49 493 August 14 1962 David W. Young et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 6 line 63 after "which" insert 111 has an average value from about 37 to 45.

Signed and sealed this 11th day of December 1962.

SEAL) LUCSIZ DAVID L. LADD ERNEST W. SWIDER Commissioner of Patents tttesting Officer 

1. A SYNTHETIC LUBRICATING OIL COMPOSITION CONSISTING ESSENTIALLY OF (1) A DIESTER SYNTHETIC OIL BASE HAVING A VISCOSITY OF ABOUT 35 TO 250 SUS AT 210* F, SAID DIESTER BEING OF AN ALIPHATIC DIBASI ACID UP TO ABOUT 12 CARBON ATOMS AND AN ALIPHATIC ALCOHOL OF UP TO ABOUT 12 CARBON ATOMS AND (2) ABOUT 5 TO 50 WEIGHT PERCENT OF A POLYESTER PREPARED BY THE REACTION OF AN ALIPHATIC DIBASIC ACID CONTAINING FROM ABOUT 6 TO 11 CARBON ATOMS WITH A POLYOXYALKYLENE GLYCOL OF THE FORMULA: 